Tham khảo tài liệu 'mcgraw hill - 2002 - w-cdma and cdma2000 for 3g mobile networks_2', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 22 Chapter 1 system with N carriers N 1 2 or 3 each individual carrier usually has a bandwidth of MHz. However for N 3 the total bandwidth required is 5 MHz including the necessary guard bands. To provide for high-speed data services say up to 2 Mb s a single carrier may have a nominal bandwidth of 5 MHz11 with a chip rate of Mc s that is 3 X Mc s . Commercial viability may require the cdma2000 technology to be introduced in different phases. For example phase 1 may use a single carrier that will support data rates up to 144 kb s. In phase 2 two more carriers may be added to provide still higher data rates. Standards have been designed to harmonize core networks of UMTS with those of GSM. Similarly packet mode data services of UMTS have been harmonized with GPRS which is a service capability of GSM 2G1. W-CDMA which is the radio interface of the UMTS Terrestrial Radio Access UTRA uses a direct sequence spread spectrum on a 5 MHz bandwidth and operates in both FDD and TDD modes. The TDMA version of the 3G system for use in North America is known as UWC-136. As shown in Figure 1-8 its evolution takes place in three phases IS-1361 IS-136 HS Outdoor Vehicular and IS-136 HS Indoor. The first phase IS-1361 provides voice and up to 64 kb s data. The per-channel bandwidth is still the same that is 30 kHz as for IS-136. However to support higher data rates 8-PSK modulation is used instead of the usual QPSK. The second phase provides data rates up to 384 kb s for outdoor vehicular operations using high-level modulation and a bandwidth of 200 kHz per channel. It should be mentioned here that ETSI has defined a standard called Enhanced Data Rates for GSM Evolution EDGE to support IP-based services in GSM at rates up to 384 kb s 20 21 . IS-136 HS for outdoor vehic-ular applications is designed to use this standard in the access network. In the third stage IS-136 HS Indoor end users may have a data rate of up to 2 Mb s with a bandwidth of MHz. The spectrum
